Guidelines for Multihomed and IPv4/IPv6 Dual-Stack Interactive Connectivity Establishment (ICE)
RFC 8421

Document Type RFC - Best Current Practice (July 2018; No errata)
Also known as BCP 217
Last updated 2018-07-19
Replaces draft-ietf-mmusic-ice-dualstack-fairness
Stream IETF
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Stream WG state Submitted to IESG for Publication (wg milestone: Jan 2016 - Submit Dual-stack Fa... )
Document shepherd Ari Keränen
Shepherd write-up Show (last changed 2016-04-07)
IESG IESG state RFC 8421 (Best Current Practice)
Consensus Boilerplate Yes
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Responsible AD Ben Campbell
Send notices to "Ari Keranen" <ari.keranen@ericsson.com>
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Internet Engineering Task Force (IETF)                      P. Martinsen
Request for Comments: 8421                                         Cisco
BCP: 217                                                        T. Reddy
Category: Best Current Practice                             McAfee, Inc.
ISSN: 2070-1721                                                 P. Patil
                                                                   Cisco
                                                               July 2018

           Guidelines for Multihomed and IPv4/IPv6 Dual-Stack
              Interactive Connectivity Establishment (ICE)

Abstract

   This document provides guidelines on how to make Interactive
   Connectivity Establishment (ICE) conclude faster in multihomed and
   IPv4/IPv6 dual-stack scenarios where broken paths exist.  The
   provided guidelines are backward compatible with the original ICE
   specification (see RFC 5245).

Status of This Memo

   This memo documents an Internet Best Current Practice.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   BCPs is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8421.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Martinsen, et al.         Best Current Practice                 [Page 1]
RFC 8421        ICE Multihomed and Dual-Stack Guidelines       July 2018

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Notational Conventions  . . . . . . . . . . . . . . . . . . .   3
   3.  ICE Multihomed Recommendations  . . . . . . . . . . . . . . .   3
   4.  ICE Dual-Stack Recommendations  . . . . . . . . . . . . . . .   4
   5.  Compatibility . . . . . . . . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   In multihomed and IPv4/IPv6 dual-stack environments, ICE [RFC8445]
   would benefit by a fair distribution of its connectivity checks
   across available interfaces or IP address types.  With a fair
   distribution of the connectivity checks, excessive delays are avoided
   if a particular network path is broken or slow.  Arguably, it would
   be better to put the interfaces or address types known to the
   application last in the checklist.  However, the main motivation by
   ICE is to make no assumptions regarding network topology; hence, a
   fair distribution of the connectivity checks is more appropriate.  If
   an application operates in a well-known environment, it can safely
   override the recommendation given in this document.

   Applications should take special care to deprioritize network
   interfaces known to provide unreliable connectivity when operating in
   a multihomed environment.  For example, certain tunnel services might
   provide unreliable connectivity.  Doing so will ensure a more fair
   distribution of the connectivity checks across available network
   interfaces on the device.  The simple guidelines presented here
   describe how to deprioritize interfaces known by the application to
   provide unreliable connectivity.

   There is also a need to introduce better handling of connectivity
   checks for different IP address families in dual-stack IPv4/IPv6 ICE
   scenarios.  Following the recommendations from RFC 6724 [RFC6724]
   will lead to prioritization of IPv6 over IPv4 for the same candidate
   type.  Due to this, connectivity checks for candidates of the same
   type (host, reflexive, or relay) are sent such that an IP address
   family is completely depleted before checks from the other address
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